1. Field of the Invention
The invention relates to a method and apparatus for gauging the spacings between successive turns of a wire helically wound on a fluid pervious, generally cylindrical body to form a wire screen for use in subterranean wells.
2. Summary of the Prior Art
Wire screens have long been employed in subterranean wells at the bottom of a production tubing string and in communication with a fluid producing formation. Such screens embody a wire helically wound around and welded to a generally cylindrical, fluid pervious body, such as a plurality of peripherally spaced rods or a cylindrical tube having a plurality of axially and angularly spaced radial perforations therein. The spacing between adjacent turns of the helical wire determines the size of particles that are permitted to pass through the screen and into the tubing string. It is very critical to the operation of all equipment disposed uphole from the screen and extending to the pipe line to eliminate particles of significant size from the flow of well fluids. It is equally important that the successive helical turns not be spaced so closely together as to constitute a barrier to the full production flow of the particular formation.
In recent years, well operators have imposed increasingly stringent requirements on the manufacturers of helically wound wire screens to adhere to prescribed spacings between all adjacent turns of the screen. Such requirements have resulted in the necessity of manually gauging both the minimum and maximum spacing of all the turns of a wire screen and, since the wire employed is normally of a width or diameter approximating 0.090 inches and the screens are ten feet or more in length, this involves a very time consuming laborious job which is never completely accurate because the entire circumference of each turn spacing is very difficult to manually gauge.
There is, therefore, a definitive need for a method and apparatus for gauging both the maximum and minimum spacing of adjacent turns of a helically wound wire screen for use in subterranean wells wherein the gauging is effectively accomplished between all adjacent turns and around the entire periphery of the screen. Such method and apparatus has not heretofore been available in the prior art.